Process of electrolytically removing scale and producing iron sulfate.



To all whom it may concern;

UNITED sTATEs PArENT OFFICE.

CHARLES J. REED, OF PHILADELPHIA, PENNSYLVANIA. PROCESS OF ELECTROLYTICALLY REMOVING SCA LE AND PRODUCING IRON SULFATE.

Be it known that I, CHARLES J. REED, a citizen of the United States, residin at Philadelphia, in the county of Philade phia and State of Pennsylvania, have invented certain new and useful Improvements in Processes of Electrolytically Removing Scale and Producing Iron Sulfate, of which the followin is a specification.

arious electrolytic methods have, been proposed for removing the oXid scale from iron sheets, rods, and wire. In some of these the iron article is made the anode in an electrolyte of acid or an acid salt. The scale is thus dissolved more rapidly than in the usual pickle bath; but the action is apt to be irregular, and solution of the iron invariably occurs. Furthermore, the gain in time is more than offset by the cost of the electric current. Inother proposed methods the iron article is made the cathode in an electrolyte which is neutral, weakly acid, or alkaline for exam-, ple, a dilute solution 'of an alkali-metal salt, an acid, or an alkali. The removal of scale, however, is slow and irregular, spots of scale being fre uentlyleft at variouspoints. Some of the sea e is also loosened by the electrolytic hydrogen and drops into the bath. In neu-' tral or alkaline solutions much of the scale is reduced to metallic iron, producing a rough irregular surface.

According to the present invention the iron article is made the cathode in an electrolyte consistin preferably,-of a strong a neous solution if sulfuric acid. The scalie is thereby reduced to a lower state of oxidation and electrolytically dissolved with the production of ferrous sulfate. An insoluble anode is employed, and sulfur dioXid is maintained in solution in the electrolyte, serving by its oxidation to both depolarize the anode and replenish the acid in solution.

In the preferred mode of procedure the electrolyte consists of an aqueous solution of sulfuric acid having a specific gravity of about 1.20, equivalent to an acid content of 27.1 per cent. The anode may be of lead and the current density at the cathode from forty to seventy'amperes er square foot. The electrolyte is referab y maintained ata temerature of a out centi rade. The sulr dioxid may be supplie directly to the electrolytic cell, as by allowin it to .rise in bubbles along the anode, or the electrolyte may be circulated between the cell and a separate vessel, into which the gas is intro Specification of Letters Patent; Application filed January 2, 1906. Serial No. 294,292.

l'atented July 31, 1906.

duced. A diaphragm-cell is preferably employed, the gas being supplied to the anodecompartment or anolyte to prevent its wasteful reduction to sulfur ,at the cathode. Under these conditions the reduction and solution of the scale on the cathode and the oxidation of the sulfur dioxid at the anode are 7 rapid and continuous. rate of supplyofthe gas the production of acid may be made to correspond with the rate of its consumption by the ferrous sulfate, the electrolyte thus being maintained at the proper concentration. In the case of a diaphragm-cell the concentration of the acid in the catholyte is maintained by diffusion and cataphoresis from the anolyte.

As the amount of iron sulfate in solution approaches saturation the electrolyte. or catholyte is transferred to a shallow pan and allowed to cool. It is preferable to reduce its By regulating the temperature to about 0 centigrade by the use of a suitable refrigerant. The iron sulfate crystallizes out, and the residual solution is returned to the electrolytic cell, preferably to the anode-compartment, no evaporation or further treatment being required v to fit it for continued use as an electrolyte.

I claim- 1. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte containing sulfuric acid and sulfur dioxid, as set forth.

2. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte consistin of a strong aqueous solution of sulfuric aci impregnated With sulfur dioxid, as set forth.

3. The process of electrolytically dissolving iron-oxid. scale from the surface of metal, which consists in passing to the metal as cathode, in an electrolyte consisting of 'a heated, strong aqueous solution of sulfuric acid impregnated with sulfur dioxid, an elec tric current of sufficient density to rapidly revmove the scale, as set forth.

4. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passin an electric current to the metal, as catho e, in an electrolyte containing sulfuric acid, and introducing sulfur dioxid intothe electrolyte, as set forth.

5. The process of electrolytically dissolv- IIO ingiron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte consisting of a strong aqueous solution of sulfuric acid, and introducing sulfur dioxid into the electrolyte, as set forth.

6. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing to the metal, as cathode, in an electrolyte consisting of a heated, strong aqueous solution of sulfuric acid, an electric current of sufficient density to rapidly remove the scale, and introducing sulfur dioXid into the electrolyte, as set forth.

7. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte containing sulfuric acid and sulfur dioxid, and recovering the iron sulfate from the resulting solution, as set forth.

8. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in passing an electric current to the metal, as cathode, in an electrolyte containing sulfuric acid and sulfur dioXid, withdrawing the resulting solution, recovering the iron sulfate therein and returning the solution to the electrolytic cell, as set forth.

9. The process of electrolytically dissolving iron-oxid scale fromthe surface of metal, which. consists in passing an electric current to the metal, as cathode, in an electrolyte containing sulfuric acid and sulfur dioxid, withdrawing and cooling the resulting solution, thereby precipitating the iron sulfate, and returning the residual solution to the electrolytic cell, as set forth.

10'. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in interposing a diaphragm between a catholyte and anolyte containing sulfuric acid, passing an electric current to the metal, as cathode, and supplying sulfur dioxid to the anolyte, as set forth.

11. The process of electrolytically dissolving ir0n-oxid scale from the surface of metal, which consists in interposing a diaphragm between a catholyte and anolyte consisting of a strong aqueous solution of sulfuric acid, passing an electric current to the metal, as cathode, heatin the electrolyte, and supplying sulfur dioxid to the anolyte, as set forth.

12. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which consists in inter )osing a diaphragm between a catholyte an anolyte containing sulfuric acid, passing an electric current to the metal, as cathode, supplying sulfur dioxid to the anolyte, and circulating the electrolyte between the cell and a precipitating vessel, as set forth.

13. The process of electrolytically dissolving iron-oxid scale from the surface of metal, which. consists in interposin a diaphragm between a catholyte and ano yte containing sulfuric acid, passin an electric current .to the metal, as cathode, supplying sulfur dioxid to the anolyte, removing and cooling the catholyte, thereby precipitating the ferrous sulfate, and returning the residual solution to the anode-compartment, as set forth.

14. The process of electrolytically dissolving iron-oX1d scale from the surface of metal, which consists in interposing a diaphragm between a catholyte and anolyte consisting of a strong aqueous solution of sulfuric acid, passing an electric current to the metal, as cathode, heating the electrolyte, supplyin sulfur dioxid to the anolyte, removing and cooling the catholyte, thereby precipitating the ferrous sulfate, and returning the residual solution to the anode-compartment, as set forth.

In testimony whereof I affix my signature in presence of two witnesses.

CHARLES J. REED. Witnesses:

JAY D. REED. M. J. REED. 

